The Research Design and Analysis (RDA) Core has four closely related broad objectives designed to enhance the research efforts of the MRDDRC investigators. The broad objectives are: (1) to provide high quality design and analysis services, (2) to provide educational opportunities to enhance MRDDRC investigators' analytical research skills, (3) to provide data management services to ensure data quality an proper data structure for analyses, and (4) to contribute to the field of mental retardation research by exploring and, where necessary, modifying statistical, graphical, and analytic techniques to maximize understanding and interpretation of mental retardation data. These objectives are described in more detail below.